It is well known that the bearing capacity of open-ended piles with a constant pile diameter used in port and harbor facilities depends on the so-called “soil plug”. On the other hand, in tapered piles which gradually decrease in diameter toward the tip of the pile, the soil plug is not likely to be occurred due to their shape, but their bearing capacity is comparable to that of straight piles. In this study, the difference in bearing capacity between straight piles and tapered piles was verified by conducting a large scale model test.
In the experiments, a series of tests from the pile penetration process to the loading test were conducted on straight and tapered piles, and the load-displacement relationship of the piles, the data of strain gauges and earth pressure gauges attached to the piles were summarized. In addition, in order to verify the effect of the soil plug on bearing capacity, an experiment was conducted to remove the plugging by vacuuming sand inside the pile during the pile penetration process. As a result of the experiment, it was found that the tapered pile was hardly affected by the soil plug, and could keep the bearing capacity even under adverse conditions where the bearing capacity of the straight pile was significantly reduced.

Key Words:large-scale model test,open-ended pile,soil plug,tapered pile,bearing capacity